Canine coronavirus (CCV) is a member of the distinct viral family of Coronavirus. Viruses belonging to this genus are known to infect a variety of animal species including man. They cause diverse diseases, such as gastro-enteritis (in swine, turkeys, mice, calves, dogs, cats and man), salivary gland infection (in rodents), respiratory disease(in man, swine, avians and dogs) and encephalitis (in young swine).
CCV was first isolated from military dogs in Germany in 1971 and has found to be highly contagious and it spreads rapidly among susceptible dogs. Usually, the CCV is ingested on materials contaminated by infectious feces. Oral infection leads to viral replication in epithelial cells of the small intestine and CCV has also been found in the intestinal lymph nodes.
The signs of the disease can develop 1-3 days following infection and include vomiting, diarrhoea, anorexia, depression and dehydration. The persistence and severity of signs is often related to stress and the presence of other viruses, parasites or bacteria. Whereas the enteric symptoms are dominant, respiratory signs including nasal and ocular discharge have also been reported.
Dogs are the only known host of the CCV. Although CCV inoculation of cats and pigs results in infection, no clinical disease will be caused by CCV in these species. There is no evidence that humans, cattle and mice are susceptible to CCV.
Cross protection studies have shown that the Coronaviruses induce little or no immunity to each other. For example, experimental infection of dogs with transmissible gastro-enteritis virus (TGEV) of pigs or feline infectious peritonitis virus (FIPV) of cat does not protect them against the effects of a subsequent CCV infection.
Coronaviruses consist of a group of enveloped viruses containing a genome consisting of a single-stranded RNA of about 30 kb. This genome encodes inter alia three important structural proteins: a spike protein (S), a membrane protein (M) and a nucleocapsid protein (N). The glycosylated spike protein S.sub.o is cleaved to form S.sub.1 and S.sub.2 in some coronaviruses. Two or three copies of each of S.sub.1 and S.sub.2 form a characteristic CCV surface structure, the spike or peplomer. The spike protein and its constituent polypeptides thereof play an important role in inducing a virus neutralizing immune response in infected animals.